1. Field of the Invention
The present invention relates to an inkjet recording head that ejects ink toward a recording medium and thereby carries out recording on the medium.
2. Discussion of Related Art
Patent Document 1 (Japanese Patent Application Publication No. 2003-159798) or Patent Document 2 (Japanese Patent No. 3267937 or its corresponding U.S. Pat. No. 6,471,342) discloses an inkjet recording head that ejects ink toward a recording medium and thereby carries out recording on the medium. The disclosed inkjet recording head includes a channel unit having a plurality of pressure chambers communicating with a plurality of nozzles, respectively; and a piezoelectric actuator that selectively changes a volume or respective volumes of an arbitrary one or ones of the pressure chambers. The piezoelectric actuator includes a plurality of individual electrodes corresponding to the pressure chambers, respectively; a common electrode that is opposed to each of the individual electrodes and may be constituted by a diaphragm; a piezoelectric layer that is interposed between the individual electrodes and the common electrode; and a plurality of electric wires that are connected to the individual electrodes, respectively, so as to supply respective drive voltages thereto. In this piezoelectric actuator, the electric wires are located, as seen in a direction perpendicular to a reference plane along which the pressure chambers are provided, in areas corresponding to areas present between the pressure chambers, such that each of the electric wires does not overlap any pressure chambers other than the pressure chamber corresponding to the individual electrode to which the each electric wire is connected. In the piezoelectric actuator, when a drive voltage is supplied to an arbitrary one of the individual electrodes via a corresponding one of the electric wires, an electric field is generated in a portion of the piezoelectric layer that is located between the one individual electrode and the common electrode, so that that portion of the piezoelectric layer is deformed. This deformation of the piezoelectric layer changes the volume of the pressure chamber corresponding to the one individual electrode to which the drive voltage is supplied, and thereby applies a pressure to ink present in the pressure chamber.
Meanwhile, recently, there has been a demand for such an inkjet recording head that satisfies both the requirement to improve printing quality and the requirement to reduce the size of the head. To this end, it has been proposed to form a plurality of pressure chambers at a high density. However, if, in the piezoelectric actuator, as disclosed by the above-indicated Patent Document 1 or 2, wherein the electric wires extending from the pressure chambers are located in the areas corresponding to the areas between the pressure chambers, the pressure chambers are formed at a higher density, then it is needed to reduce the areas in which the electric wires are located and decrease a pitch at which the wires are provided. And, if the pitch of provision of the electric wires is decreased, then the production cost of the piezoelectric actuator is raised, the production yield of the same is lowered, and the reliability with which the electric wires are electrically connected to the individual electrodes so as to supply the drive voltages thereto is lowered.